VIRTIO SCSI vs VIRTIO SCSI single

[mir]

Can anybody explain the big performance difference between VIRTIO SCSI and VIRTIO SCSI single especially when using iotread=0 and iothread=1?

read : io=1637.7MB, bw=39596KB/s, iops=6491, runt= 42350msec  VIRTIO SCSI iotread=0
read : io=1637.7MB, bw=41136KB/s, iops=6744, runt= 40765msec  VIRTIO SCSI single iotread=0
read : io=1637.7MB, bw=36911KB/s, iops=6051, runt= 45431msec  VIRTIO SCSI iotread=1
read : io=1637.7MB, bw=53724KB/s, iops=8808, runt= 31213msec  VIRTIO SCSI single iotread=1

write: io=420263KB, bw=9923.6KB/s, iops=1625, runt= 42350msec VIRTIO SCSI iotread=0
write: io=420263KB, bw=10309KB/s, iops=1689, runt= 40765msec  VIRTIO SCSI single iotread=0
write: io=420263KB, bw=9250.6KB/s, iops=1515, runt= 45431msec VIRTIO SCSI iotread=1
write: io=420263KB, bw=13464KB/s, iops=2206, runt= 31213msec  VIRTIO SCSI single iotread=1

 

[fireon]

Interested too.

 

[spirit]

Virtio scsi single use 1 scsi controller by disk , virtio scsi classic use 1 controller for 16disk. Iothread only work by controller.

 

[mir]

Virtio scsi single use 1 scsi controller by disk , virtio scsi classic use 1 controller for 16disk. Iothread only work by controller.

So iothread with virtio scsi is pointless or do I misunderstand you?

 

[spirit]

So iothread with virtio scsi is pointless or do I misunderstand you?

Yes pointless (at least un current qemu implémentation ) vitioscsi single has been added for iothread and multiqueues , which are both controller properties . (Same for virtioblk, which by default have akways 1 controller by disk)

 

[pmra]

...pretty old thread but best search result for "VIRTIO SCSI vs VIRTIO SCSI single"

My question: "Shrink Qcow2 Disk Files" says controller must be set to "VIRTIO SCSI". Is that just outdated info and "VIRTIO SCSI single" is fine as well or does it have to be "VIRTIO SCSI"?

 

[fireon]

...pretty old thread but best search result for "VIRTIO SCSI vs VIRTIO SCSI single"

My question: "Shrink Qcow2 Disk Files" says controller must be set to "VIRTIO SCSI". Is that just outdated info and "VIRTIO SCSI single" is fine as well or does it have to be "VIRTIO SCSI"?

That's a good question. Make a backup and test it for us... I'm curious myself...